In the prior art of proportional pressure relief valves it is known to use a pilot type valve to control and vary the maximum pressure allowed in a fluid line. In such pressure relief valves, a spring is used to bias a pilot valve closed, the effective applied force of the spring being variable to vary the effective maximum pressure the pressure relief valve allows to exist in the fluid line with which it is being used.
However, heretofore, most, if not all, such pressure relief valves have utilized some form of manual or mechanical control, in which, for example, a rotatable, threaded member was used to vary the spring tension on the pilot valve and hence the pressure level in the system. Such a manual or mechanical approach greatly limits the possible applications in which such pressure relief valves could be used.
In contrast, in the present invention a pressure relief valve has been designed in which the action of the pilot valve is electrically controlled, allowing such a valve to be used in systems which can effectively use, for example, computer based controls, greatly expanding the possible applications for such a system.